The present invention relates to devices for detecting, monitoring and/or measuring low-level concentrations of certain materials within a complex matrix stream or aggregation of flowable materials. In one of several, more particular aspects, the present invention relates to such devices which employ permeation membrane or diffusion membrane tubing in some fashion to collect and isolate these certain materials from within the stream or aggregation.
Tubular membranes have been suggested for use in this capacity in a number of analytical devices, and are particularly of interest for use in separating out those components of a complex stream or aggregation which might adversely affect a gas or liquid chromatograph or other analytical device if one attempted to analyze the stream or aggregation directly.
Because of the harsh sampling environment presented by many process streams and because of the fragility of the suitable tubular membranes, the previously known devices employing such tubular membranes have very largely been designed to operate on but a portion of the larger stream or aggregation.
Commonly assigned U.S. Pat. No. 5,317,932 describes a device which is amenable to sampling from difficult process streams or aggregations by direct insertion. This feature represents a significant improvement over the previously-known devices. One formerly unresolved problem that the inventors have noted with respect to known direct insertion devices relates to the time taken to obtain a sample of material under review from the source to the analytical device. If the analyzer is in close proximity to the direct insertion device then single conduit direct insertion devices are quite effective. If, on the other hand, the analyzer is located some distance from the direct insertion device then it could take a significant length of time to move an amount of the material under review to the analyzer. This lag time is usually objectionable.